Field of Invention
The present invention relates generally to an apparatus and method for wireless networks, more specifically towards programmable distribution of handoff control, which comprises controlling how wireless devices handoff between different base stations and/or access points.
Discussion of Related Art
Controlling how wireless devices associate with which wireless access points and/or base stations is an essential part of any wireless network that supports device mobility in and out of the network as well as within the network. Wireless handoffs allow a mobile user equipment (UE) to move from a current wireless access point or base station to a targeted wireless access point or base station. In general, the handoff decision can be taken by the network with or without using the measurements from the UE, or it can be taken by the UE.
In Long Term Evolution (LTE) networks, UE reports the signal strength measurements from the current base station as well as the neighboring base stations to its current base station. Based on these reported signal strengths, if the signal quality at the current base station drops below a certain threshold and the signal quality at another base station raises above a certain threshold, the other base station becomes a candidate base station. Among the candidate base stations, the current base station picks the target base station and initiates an admission control procedure by sending a handoff request to the target base station. Target base station can either admit the handoff request or deny it based on its current load. If admitted, the current base station informs the UE to disconnect from the current base station and reconnect to the target base station.
In WiFi networks, UEs monitor the available WiFi networks and initiate the association request based on the locally available WiFi profiles. Any reassociation decision to another WiFi network is taken by the UE. Mobility among the access points of the same WiFi SSID is handled seamlessly as there is no need for explicit time synchronization. UEs keep a dynamic list of WiFi networks that they can attach with. The list can be generated and modified by the owner of the device. Trusted third parties such as network operators or over the top service providers can also configure this list. Using standard solutions such as 802.11u, UEs can acquire information about which WiFi access points they can connect to dynamically as they roam before they make an attachment decision. Access Network Query Protocol (ANQP) provides the signaling framework between UE and WiFi APs to reach trusted servers to exchange information about the WiFi access in the current location of UE.
Access Network Discovery & Selection Function (ANDSF) is another standards based solution (3GPP TS 24.312) that sets the priorities of different access schemes on a per UE or per IP flow basis depending on the device capabilities (e.g., whether it can support multiple interfaces at the same time or only one interface at a time). Time of day, location, and application type are among the few conditions that can be used to set different prioritization across access networks.
In 2G and 3G CDMA networks, UEs attach to multiple base stations at the same time using different spreading codes and can receive the same data simultaneously from multiple base stations. Base stations that UE receives from form a dynamic set, and based on the quality of signals, new base stations are added or existing base stations are removed from said set.
Cooperative Multi-Point Transmission (COMP) techniques are part of LTE networks, where same or distinct payloads can be transmitted simultaneously from multiple LTE base stations using the same or distinct resource blocks.
In publication US 20130077482 A1, inventors disclose a method of handoff between a cellular base station and a collocated WiFi access point. The method collects information related to the cellular network and the WiFi network that comprises collecting real time performance data of the cellular and the WiFi network at the cellular base station and at the WiFi access point, wherein the real time performance data includes one or more of the following: a level of traffic congestion, a degree of latency, a level of throughput, and a load-balancing metric. Further network cost and operator policies are also considered as part of this handoff decision.
In U.S. Pat. No. 8,588,790 B2, inventors disclose a handoff method that decides not to handoff a UE from a macro cell to a small cell based upon the speed of the UE. If no handoff is requested by UE, macro cell assigns a macro cell only resource block to the UE while UE is residing inside the small cell area.
In U.S. Pat. No. 8,948,767 B2, inventors make cell reselection/handoff parameters such as hysteresis parameters, time-to-trigger (TTT) values, offset parameter, etc. programmable on a per small cell and UE basis by collecting the counts of cell reselection/handoff between a particular small cell and a particular macro cell and adapting the cell reselection/handoff parameters based if these counts exceed a threshold determined by the handoff management function.
Embodiments of the present invention are an improvement over prior art systems and methods.